1. Field of the Invention
The invention relates to an ablation apparatus for intracardial heart treatments with a high-frequency energy source (RF source for short) and to a method for operating the apparatus.
2. Description of the Prior Art
During the ablation, tissue layers in the heart are denatured by means of a flexible catheter in order to eliminate disturbances of the stimulus conduction system. Disturbances of this kind manifest themselves as heart arrhythmias (e.g. tachycardia). The disturbing stimulus conductors are localized and then intentionally interrupted using the ablation catheter. The tissue lesion carried out for the interruption is performed with the help of high frequency alternating currents of an RF source. The power output of the RF source is adjusted by means of a temperature regulation in such a manner that the cells are necrotised, but that the cellular composition (the tissue) is not destroyed and that no coagulation takes place at the pole giving off the energy.
Ablation apparatuses are composed of an apparatus part which contains the RF source and at least one catheter which is connected to the RF source and has one or more poles which give off energy.
Different types of catheters are used, for example those which differ in the temperature sensors at the poles. These sensors can be thermistors or thermoelements.
As a result of inhomogeneities in the heat conduction, a temperature distribution with different temperatures can arise on the pole. The temperature sensor measures an average temperature and thus local overheatings can arise on the pole. The temperature relationships on the pole can be better measured with a plurality of temperature sensors.
The pole can be assembled from a plurality of separate segments, which are all connected to the same RF source and each of which contains a separate temperature sensor. The ablation can also be carried out using two catheters which are separate but connected to the same RF source and act on the same tissue location. In this case the poles of the two catheters represent two segments of a common pole or else two opposite poles.
Catheters are also known which have no temperature sensors.
There is also a large variety of catheters which differ with respect to different sensor types (when there is a sensor present) and/or which differ with respect to the number of sensors, which can also be zero.
In known ablation apparatuses (e.g. the Cordis-Webster/Stockert "EP shuttle") the catheter type must be set manually. This manual setting is an action which must be performed specially by the user and which can lead to an error in the operation as a result of a confusion of the catheters.
U.S. Pat. No. 5,383,874 describes catheters with codings which make the type of the catheter recognisable by the apparatus. These catheters can however be used only with apparatuses which are capable of deciphering this coding. Conversely, only catheters which contain this coding can be used with these apparatuses.